This invention relates to thermoplastic polymer alloy compositions which exhibit excellent low temperature properties coupled with heat and scuff resistance and to a process for producing such compositions.
For many years films and laminates of polyvinyl chloride (PVC) resins have found utility in the production of thermoformed articles including, for example, videotape cases, food packaging, and beverage containers. In the automotive field PVC has been employed extensively in the fabrication of interior sheathing for automobiles, for example, in instrument panel skins, door panels, roof liners, and seat covers. Although performance has been adequate, there are certain disadvantages inherently associated with use of PVC in these applications. In particular, large amounts of plasticizers must be incorporated into the resin in order to enhance flexibility and low temperature properties, as well as to provide a soft surface texture. However, as a result of the high temperatures to which the interiors of parked automobiles are subjected, the plasticizers have a tendency to migrate to the surface of the PVC films and consequently the PVC sheathing becomes brittle. In addition, a film of plasticizer is gradually deposited on the interior surfaces of the automobile, particularly on the interior surfaces of the windows.
A more recently recognized disadvantage of the use of PVC concerns the difficulty of disposal and recycle of the resin. Incineration results in generation of significant quantities of hydrogen chloride and heavy metal redidues. In addition, the resin is not compatible with other plastics used in the manufacture of automobiles, thereby creating problems during recycling operations.
Non-halogenated thermoplastic alloy compositions having good high temperature properties are known in the art, for example the polyolefin/ionomer blends disclosed in U.S. Pat. No. 4,871,810 or the blends of partially crosslinked ethylene/alpha-olefin copolymers with reaction products of ethylene copolymer ionomers and olefin/epoxy copolymers, disclosed in U.S. Pat. No. 4,968,752. Such compositions, however, are either deficient in softness of scuff resistance.
Consequently there is a need in the art, especially in the automotive field, for a material which combines the low and high temperature resistance properties of plasticized PVC, can be recycled easily, and exhibits scuff resistance and softness equal or superior to that of plasticized PVC.